As explained in U.S. Pat. No. 4,103,490, issued to Alexander M. Gorlov on Aug. 1, 1978, the patent and its references being incorporated herein by reference, there have been many systems utilized for the harnessing of tidal power. In that patent, a single tidal chamber is utilized in which a housing is mounted on the ocean bed with ports of ingress and egress near the bottom or lower part of the housing, through which tidal waters may flow. Positive air pressure is built up in the housing by rising tides, and partial vacuums are built up in the housing by falling tides. In the abovementioned patent, the positive air pressure or partial vacuum at the top of the housing is connected through auxiliary high pressure and low pressure chambers to a two-state revolving valve having two input ports and two output ports. The output ports may be connected to a reciprocating air motor so that low level energy in the last one foot or so of the tide may be made to do useful work.
As will be seen, while this system works well for small scale operations, its capacity is limited by the physical size of the housing. Only such potential energy as can be stored in the height of water within the housing can be used during any one tidal cycle.
In a second U.S. Pat. No. 4,095,423, issued to Alexander M. Gorlov on June 20, 1978 and incorporated herein by reference, a similar system is described in which a dam structure is used which does not require of roof over four walls. Here, rather than using an air valve, a water valve is employed.
It is a feature of the second patent, as well the first patent, that relatively low amounts of tidal fluctuation can be made to do useful work. Thus even the last foot of tide can power a reciprocating air engine, even if the water head is too low to run a conventional turbine.
While this second system works well for small scale plants, the size and flow capacity of the valve limits the amount of water than can do useful work during a tidal cycle.
In general, if one wishes to harness the tides at the Bay of Fundy, a system must be devised to handle many millions of cubic feet of water per hour. By so doing, thousands of megawatts of power can be produced. To accomplish this the housing of the first patent would have to be as large as the Bay of Fundy if all available energy were to be extracted. As will be appreciated, the cost of construction of extremely large housings is prohibitively high if one were to attempt to harness all of the water head available in a tidal creek, bay or reservoir.